A flip-chip integrated circuit package generally includes an integrated circuit die mounted on top of a package substrate using available backend assembly processes. Prior to assembly, the substrate may be warped. This warpage may be categorized by a variety of warpage profiles. The warpage is a result of the baking step in the package assembly manufacturing process. The warpage profiles may be classified into different groups that include a ‘crying’ (convex) warpage profile, a ‘smiling’ (concave) warpage profile, a ‘potato-chip’ (wavy) warpage profile and a ‘flat’ warpage profile.
Among all the pre-assembled package substrates, almost 7-11% of pre-assembled package substrates may have a severe ‘crying’ warpage profile (i.e., warpage level of approximately 50-100 microns (μm)), which are often rejected. Package substrates with a severe ‘crying’ warpage profile are rejected because such package substrates generally have reliability concerns and, in some cases, may adversely affect the functional performances of the resulting integrated circuit packages. Such rejection may usually cost a lot to the integrated circuit package manufacturer and this may eventually increase the cost of manufacturing integrated circuit packages.